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I've owned a place for about a year now and was just having some work done on my heat pump.

I've got a contractor, I really like and trust, though I don't have much history with him. I'd like to run what he's told me past some proffesionals, not so much to get a second opinion as to get a supplement to what he's told me.

Initially he replaced the compressor in the heat exchanger and repaired a leak in the return piping to the compressor.

In doing so he noticed the pressures on the return line were much higher than they should have been. Looking for the source of this problem, he's found two issues.

First, the heat exchanger is too large for the furnace. The heat pump is a Trane HP26-036-7P and the furnace is a CB29M-41-1P which don't match up according to ARI tables in Trane's engineering handbooks.

The other problem is that he doesn't think the installer filled the copper lines with an inert gas when soldering them together and the interior of the pipe is flaking off and plugging up the expansion valve.

He'll be replacing the expansion valve this week and will try to clean out that line.

My question is how poorly will the mis-sized units function together? He says it will do better in cooling than heating? Are we talking 80% efficient or 40% efficient?

Also has anyone else had similar problems with copper lines not being installed right and then plugging up the expansion valve?

First, by heat exchanger is he refering to the indoor coil? Second, yes weld crap can get to the metering device if nitro wasn't used during brazing. Have him put a bi-flow filter drier about 6 inches from the expansion valve. Don't forget there is another orifice out by the condenser for the heat cycle. Systems should be matched, and you have to be an engineer with all the figures to tell you exactly how much effiency it will lose.

If everything was always done "by the book"....the book would never change.

In a heatpump, the liquid line is the liquid line(sm copper line) in both heating and cooling, just flowing refrigerant in different directions. The suction line(big copper line) is the suction line in cooling mode, and the hot gas line in heating mode. I repeat, he has to clean out both metering devices and install the new filter drier.As far as cleaning one line at a time, that won't cut it because as soon as you start it up you have the remaining crap distributed through the entire system unless the drier catches it.

If everything was always done "by the book"....the book would never change.

An update

Just wanted to pass on an update to everybody here. Sorry it's been a little while.

When the contractor was out replacing the expansion valve at the furnace he noticed that I had the "Green slime" and that the whole system would have to be replaced.

Luckily, my wife and I were at a position to be able to have the additional work done at now. Which they completed just last week, including replacing the furnace with a unit sized for the heat exchanger.

We also had them replace the thermostat while they were doing the work.

Since then the house has been amazingly better. It holds a steady temperature and the furnace isn't running all the time.

As an aside, I've heard some other people say that they had bad experiances with the company whose name was on the original unit. From what I can tell, I'm fairly certain they are out of buisness by now.